Development of microsatellite markers for the bracken fern, Pteridium aquilinum

We isolated eight novel polymorphic microsatellite loci from Pteridium aquilinum. These loci were characterized in 30 individuals, one from Bolivia, two from Peru, one from the USA, one from Japan, and 25 from Northeast China to Southwest China. The number of alleles per locus ranged from two to seven. The observed heterozygosity (H(O) ) ranged from 0.000 to 0.600 with an average of 0.3051, and the expected heterozygosity (H(E) ) ranged from 0.0966 to 0.7780 with an average of 0.4267. One locus deviated from Hardy-Weinberg equilibrium and four pairs of loci were found to be in linkage disequilibrium. These polymorphic loci will be useful in the study of the population genetic structure of Pteridium.     

Effects of cyanogenesis in bracken fern (Pteridium aquilinum) on associated insects

Abstract. 1. The relationship between cyanogenesis in bracken fern and the insect fauna feeding on the plant was investigated over a 3 year period. The most common insects between May and July, while cyanide levels were high, were the sawflies Strongylogaster impressata Provancher, S.multicincta Norton, Aneug-menus fzavipes (Norton), the aphid Macrosiphum euphorbiae (Thomas) and a microlepidopteran species of Monochroa .
2. Collections of insects from cyanogenic and acyanogenic fronds showed significantly fewer sawflies on the cyanogenic fronds. The aphid and the microlepidopteran were randomly distributed with respect to cyanogenicity.
3. Feeding tests for two of the sawfly species ( Simpressata and Smulticincta ) showed that larvae grew more slowly and had a higher mortality when raised on cyanogenic fronds than on acyanogenic ones.
4. Field collected cyanogenic bracken fronds were found to have sustained less damage from chewing herbivores compared with acyanogenic fronds.     

Ultrastructural studies on oogenesis in symphyla

Summary In the oocytes of Hanseniella nivea, cortical granules are formed in the peripheral ooplasm during late stages of oogenesis. Single Golgi elements are involved in the process. Concurrent with the formation of cortical granules is the appearance of a chorion on the oocyte surface. Precursors of this envelope are most likely synthesized by follicle cells.     

Ultrastructural studies on oogenesis in Symphyla

Summary The paired ovaries of Symphyla are sac-shaped. Their interior is filled with synchronously developing oocytes surrounded by a simple follicular epithelium. Previtellogenic oocytes have spherical or oval nuclei, the latter containing a large number of small nucleoli. Part of the nuclear surface is covered by a thick coat made up of a granular substance of medium electron density. The coat is penetrated by cisternae of the smooth endoplasmic reticulum. Micropinocytosis is the principal source of yolk in Symphyla; a small amount of yolk material arises within the mitochondrial cristae. Vitellogenic oocytes are characterized by a highly active rough endoplasmic reticulum synthesizing a material, probably lipoprotein in nature, which is incorporated into lipid droplets.Supported by Government Problem Grant II-1.3.13. The author is grateful to Dr. F. Kaczmarski of the Medical Academy, Kraków, for the use of EM facilities in his laboratory and to Dr. W. Hüther, Ruhr-Universität, Bochum, for the identification of the specimens     

Ultrastructural Aspects of Sporogenesis in a Fern, Pteridium aquilinum (L.) Kuhn

The meiotic process of sporogenesis in Pteridium is accompaniedby a regular cycle of ultrastructural events. These includethe dedifferentiation and redifferentiation of organelles, andthe elimination and restoration of ribosomes. Although similarin nature to corresponding stages in other land plants, sporogenesisin Pteridium provides several unique features. During prophase the plastids pass through a stage during whichno envelope can be resolved at the periphery of the stroma.They appear to survive this period and there is no evidencethat plastid lineage is broken from primary archesporium tospore. The plastid cycle is accompanied by the presence of theiron-protein complex phytoferritin. The repopulation of the spore cytoplasm with ribosomes, followingthe prophase elimination, is achieved through the agency ofnucleoloid-like bodies. These bodies, however, are not synthesizedwithin the nucleus, but form within membrane-bound regions ofthe early prophase cytoplasm. Prophase is also characterized by the development of nuclearvacuoles, expansions of the perinuclear space, which progressivelyramify through the karyoplasm prior to the dissolution of thenuclear envelope at metaphase I. The significance of these events, their similarities with, anddifferences from, comparable stages of meiosis in other plantsare discussed. Pteridium aquilinum (L.) Kuhn, bracken, meiosis, sporogenesis     

Ultrastructural and cytochemical studies on the connective tissue of chaetognaths

The hydroskeleton plays a central role in the architecture of the trunk of the Chaetognath. Its fibrous part is composed by a ‘basement membrane’ which separates the epithelial and nervous level from the locomotory muscle and other tissues which surround the general cavity. This structure corresponds to a dense connective tissue sheath; together with the aqueous phase of the general cavity it constitutes the main part of the hydroskeleton. The axes of the lateral and caudal fins are extensions of this connective tissue; they are rich in ground substance and contain several kinds of fibrils and granules.The ‘basement membrane’ is made of a network of densely packed parallel layers of collagen fibrils which form helices which wrap around the trunk. The collagen fibrils of this connective stratum are sandwiched between two basal lamina; they are embedded in a reduced extracellular matrix whose components are closely related to the architecture of the collagen fibrils. In the core of the fin, the ground substance is very abundant and classical cross-striated collagen fibrils are not to be found. A compact fibrillar transition zone is to be noted between the dense connective stratum surrounding the body and the hyaline axis of the fins. In this zone, no crossbanded collagen fibrils are to be seen.The hydroskeleton and the fins show variations within the phylum. They could be related to speciation, and the ancestral pathway of the phylum. Furthermore these variations are related to the general problem of the evolution of the extracellular matrices and collagen molecule itself.     

Bracken fern (Pteridium aquilinum L. kuhn) promotes an open nitrogen cycle in heathland soils

Background and Aims

In spite of the broad array of studies conducted on the ecology of bracken fern (Pteridium aquilinum (L.) kuhn), there is currently only a limited understanding of how P. aquilinum alters the soil environment in which it succeeds. P. aquilinum is one of the world’s most aggressive invasive species and is known to effectively invade conservation priority habitats such as Calluna vulgaris (L.) heathland. The aim of this study was to evaluate differences in soil properties between intact stands of C. vulgaris and neighboring P. aquilinum to assess how P. aquilinum alters soil N transformations in a manner that might promote its success.

Methods

Replicate plots in five independently paired stands of P. aquilinum and C. vulgaris were established on land in which P. aquilinum is actively invading. Soils under the two plant types were evaluated for total N, mineralisable N, net nitrification, nitrifier activity, denitrification enzyme activity, polyphenol N complexing capacity, and resin sorption of inorganic N.

Results

Soils under P. aquilinum were consistently higher in NO₃ ^- and NH₄ ⁺ concentrations compared to C. vulgaris. Extractable organic and inorganic N concentrations for soil under P. aquilinum were respectively 65 %, 77 % and 358 % greater in amino N NH₄ ⁺-N and NO₃ ^--N compared to that under C. vulgaris. In-situ net nitrification (NO₃ ^- sorption to ionic resins) was found to be nearly 300 times greater under P. aquilinum than under C. vulgaris.

Conclusions

P. aquilinum alters the soil environment as to create an inorganic N-rich environment that is favorable to its growth and development.     

Ultrastructural and cytochemical studies on the cytodifferentiation of duodenal endocrine cells

Summary The development and cytodifferentiation of endocrine cells that produce the gastrointestinal hormones gastrin, cholecystokinin and secretin have been studied by a combined fluorescence-cytochemical, immunocytochemical and ultrastructural approach. The results show that, during development, several ultrastructurally distinct cell types exhibit COOH-terminal gastrin and cholecystokinin immunoreactivity. Furthermore, some cells simultaneously contain both gastrin- and cholecystokinin-specific antigenic determinants. Studies on the time course of development of gastrin and cholecystokinin cells, together with the above-mentioned data, suggest that gastrin cells may be converted into cholecystokinin cells in development. During this period, gastrin, cholecystokinin and secretin cells store the biogenic monoamine, 5-hydroxytryptamine a feature not displayed by the adult counter-parts of these cells. In the adult duodenum, characteristic enterochromaffin (EC) cells store 5-hydroxytryptamin for which, evidence for a possible hormonal role has been presented. Taken together, our data indicate that the differentiation of duodenal endocrine cells occurs in distinct steps, each involving a restriction in the biosynthetic repertoire of the cell.     

Ultrastructural studies of oogenesis in some european amphibians

Summary Oogenesis was studied in adult Triturus vulgaris (Urodela) with the electron microscope. The oocytes investigated ranged between 50 m and 1600 m in diameter.Two types of yolk platelet formation were found. Since both types involve the incorporation of high numbers of pinocytotic vesicles they are believed to be of an extraoocytic origin. On the basis of the order of their appearance they were named primary and secondary yolk.Five different types of vesicles were found, which participate in a variety of activities, such as yolk formation and the formation of the Golgi apparatus. They originate from four different sources, namely the nuclear membrane, the cytoplasm in connection with ribosome-like particles, the Golgi apparatus and the plasma membrane through pinocytosis. The results obtained were discussed especially with respect to differences found between the anura and the urodela, such as the presence or absence of cortical granules or equivalent structures.The authors wish to thank Prof. Dr. K.S. Ludwig for his valuable criticism and encouragement during the course of this study, Messrs. H. Boffin, C. Evers and Miss D. Lovri for their capable technical assistance.     

Ultrastructural and cytochemical aspects of oogenesis in Castrada viridis (Platyhelminthes, Rhabdocoela).

The heterocellular female gonad of the typhloplanoid Castrada viridis consists of a single germarium and two rows of vitellaria. The germarium, composed of a germinative zone and a growth zone, is surrounded externally by a layer of accessory cells the function of which is hypothesized in this study. The main feature of oocyte differentiation is the synthesis of small electron-dense inclusions produced by the rough endoplasmic reticulum (R.E.R.) and Golgi complex. The electron-dense content of the egg inclusions reacts positively to the cytochemical test used to detect polyphenols and is only partially extracted following incubation in protease. The genesis, composition, and peripheral location of egg inclusions in mature oocytes suggest that they could represent residual eggshell granules. The presumed function of eggshell granules is discussed and their fine morphology is compared with that observed in other neoophoran Platyhelminthes.     

Ultrastructural and cytochemical studies in the mantle of Anodonta cygnea

The large central region of the mantle of Anodonta cygnea was studied using transmission and scanning electron microscopy (TEM and SEM) for ultrastructural analysis and light microscopy (LM) and TEM for cytochemical analysis. X-ray diffraction studies of the organic matrix pellicle deposited on the inner surface of the shell were also carried out. Two groups of columnar cells presenting desmosomes on the apical region were observed in the outer epithelium. One group secretes a structural and neutral mucopolysaccharide (MPS) identified with chitin, normally excreted to form the organic matrix of the shell. Another group presents numerous cytoplasmic vesicles and constitutes the predominant cells of this epithelium. Two different types of mucous cells were found in the inner epithelium. One type secretes a faintly acid mucopolysaccharide (MPS) with sulphate groups and another type secretes an association of this polysaccharide with a neutral MPS. Staining for sulfhydryl groups (probably cysteine) was also positive, suggesting the presence of proteoglycans in these secretions. A third type of cells was also observed presenting a very different ultrastructural aspect (columnar form) without large secretion masses. They may correspond to the replacing cells in this highly secretory epithelium. Elastic fibers were found on the base of the outer epithelium and amoebocytes were observed in the interepithelial tissue.     

The effects of cutting and herbicide treatment on Pteridium aquilinum encroachment

Abstract. Pteridium aquilinum (bracken) encroachment is an important factor in the loss of certain habitats in the United Kingdom. However, no information exists as to whether prevention of encroachment is a cost‐effective strategy for Pteridium management. Conventional methods for the control of Pteridium (cutting, asulam application) were tested at one site (Levisham) to quantify their ability to prevent or delay encroachment and to affect the vigour of the Pteridium at the edge of the stand. The effects of encroachment and asulam application on the vegetation present were monitored at a second site (Ramsley), where techniques commonly used for moorland restoration were employed in combination with asulam application. Cutting once per year or a single application of asulam delayed the advance of the Pteridium front. At Levisham, the untreated front advanced 2.7 m in 5 yr, while in the same period the cut front advanced 0.88 m and the sprayed front was 1.5 m behind its initial position. At Ramsley, the untreated front invaded 1.8 m in 5 yr, and the sprayed front was again 1.5 m behind its starting position. Both spraying and cutting reduced frond biomass, frond cover and rhizome biomass. Herbicide spraying prevented the loss of Calluna vulgaris, though the restoration treatments had little effect. The merits of a balanced targeting of control on encroaching fronts or Pteridium at the stand level are discussed for different situations.     

蕨菜黄酮苷元的组成及含量测定研究

以80%乙醇浸提经乙醚脱脂预处理的干蕨菜粉,减压回收乙醇得浓缩液.浓缩液以8%硫酸沸水浴水解3 h后,加入20%NaOH中和至弱酸性,过滤,滤渣以三氯甲烷索氏提取获总蕨菜黄酮苷元.TLC法检测总黄酮苷元的组成,HPLC法测定其主要苷元的含量.结果表明,通过酸水解获得总蕨菜黄酮苷元,其主要成分为山奈酚,含量约占蕨菜干重的1.9%.     

Vegetation development on moorland after control of Pteridium aquilinum with asulam

Abstract. A range of moorland sites in the North York Moors National Park were surveyed where Pteridium aquilinum has been sprayed once with the herbicide asulam between 1 and 7 yr before. The regeneration of both P. aquilinum and the moorland vegetation were studied. The latter was variable and much slower than reported for lowland grassland or heathland, with a large proportion of the developing plant cover consisting of mosses, especially Campylopus introflexus. This slow rate of revegetation was primarily due to the paucity of micro-sites offered for germination in dense P. aquilinum litter, the poor establishment of seedlings in this litter and its slow breakdown. The consequences of this slow and variable development of vegetation to moorland restoration are discussed.     

Ultrastructural,cytochemical and functional studies on the eosinophilic granulocytes of larval lampreys

Summary Blood from larval lampreys (ammocoetes) contains a small number of eosinophilic granulocytes which are formed in the protospleen and kidney. Both immature and mature forms of this cell type are present in the blood and these are easily identified from other cell types due to the prominent eosinophilic granules that fill the cytoplasm. Ultrastructurally, these granules are electron-dense, largely unstructured, Golgi-derived and contain acid phosphatase but not peroxidase. Eosinophilic granulocytes ingest bacteria but fail to internalise colloidal carbon. The functional and phylogenetic significance of these cells is discussed.     

Ultrastructural and cytochemical studies on the developing adhesive disc of Boston Ivy tendrils

Summary Ultrastructural observations of the immature adhesive disc from tendrils of Boston Ivy showed that the peripheral cells, which are the presumptive contact layer, contain vacuoles of varied sizes which are filled with electron-dense aggregates. In small vacuoles, these deposits were appressed to the tonoplast and fusion of these small vacuoles with the large vacuoles apparently occurs. Cells from the central zone were largely parenchymatous. The vacuoles of many of these parenchyma cells contained electron-dense spheres and hemispheres of material either appressed to the tonoplast or within the vacuole lumen. In these cells, the vacuole-cytoplasm interface was characterized by a filiform network of interconnected membranes. Positive reactions with reagents for the identification of polyphenols indicate that the vacuoles of nearly all the peripheral cells and scattered cells of the central zone contain tanniniferous substances. Insoluble carbohydrates also occur in the vacuoles of the peripheral cells, but they contain little or no protein or lipid.     

蕨菜乙醇提取物的Ames试验研究

目的：研究蕨菜乙醇提取物的致突变作用,为蕨菜的开发利用提供一定依据;方法：制备蕨菜乙醇提取物,采用Ames试验方法,以50μg/皿敌克松作为诱变剂,分别添加提取物50、100、200、400、800μg/皿,统计回变菌落数;结果：受试物各剂量组回变菌落数均未超过自发回变菌落数的2倍,且无剂量-反应关系;结论：在本实验条件下,蕨菜乙醇提取物无致突变作用.